In order to improve the performance of a golf club beyond the current design constraints, golf club designers are often required to think outside the box and experiment with unconventional golf club designs. One example of this type of forward thinking is the recent usage of a face insert that is made out of a different material to replace the striking plate portion of a golf club head. These face inserts can be made out of a completely different material than the remainder of the body, allowing a golf club designer to improve durability of the golf club head, increase COR of the golf club head, and generate more discretionary weight within the golf club head. More specifically, the face insert may be made out of a titanium material that is lighter and more durable, resulting in improved durability, increased COR, and better weight distribution. Durability, weight savings, and additional COR are all important performance factors of a golf club that need to be considered when designing a golf club head to properly incorporate such a face insert design.
U.S. Pat. No. 5,362,055 to Rennie ('055 patent) illustrates one of the earlier attempts to utilize a face insert manufactured independently of the body in a metal wood type golf club head. More specifically, the '055 patent discloses a metal wood that has a nonmetallic insert secured to a cavity formed in the ball face insert and reinforced by ribs on the interior of the face and the walls of a cavity formed in the club face insert. The insert is secured in the cavity by adhesion which is enhanced by channels formed in the insert cavity and hollow columns formed in the insert.
U.S. Pat. No. 3,970,236 to Rogers ('236 patent) illustrates the same concept of utilizing a face insert that is manufactured independently of the remainder of the body, but in an iron type golf club head. More specifically, the '236 patent discloses a method of manufacturing that comprises casting a head having a hosel, neck, and body dependent thereon and providing the body with an open cavity in its face that extends from at least one edge thereof across a substantial portion of the face and to a first depth therein. The plate is preferably fused to the head by an electron fusion step to produce a homogenous head having an internal cavity.
In order to further push the envelope of the design constraints of a golf club, golf club designers have improved upon the usage of a face insert by creating inserts that have a variable face thickness. Having a face insert that has variable thicknesses is advantageous and desirable because it allows strategic areas of the face to deflect as a uniform body when impacting a golf ball, yielding a more evenly distributed ballspeed across a greater region of the face insert.
U.S. Pat. No. 6,638,182 to Kosmatka ('182 patent) illustrates one of these attempts to vary the thickness of the face insert by disclosing a golf club head having a thin face insert with a smooth exterior surface and a thin layer disposed on the exterior surface. The face insert has a thickness in the range of 0.010 inch to 0.200 inch, and the thin layer has a thickness in the range of 0.003 inch to 0.050 inch. The face insert may have a uniform thickness or a variable thickness.
Despite all of the advantages of utilizing a face insert made out of a separate material independently and separately from the body of the golf club head, utilizing such a face insert comes with significant design challenges. More specifically, because the face insert of the golf club head is the part of the golf club head that is subjected to the most extreme stress, connecting a face insert to the body of the golf club head at such extreme stress areas requires a significant bond strength. U.S. Pat. No. 7,479,070 to Hirano ('070 patent) discusses and confirms the extreme amount of stress at the face insert of the golf club head by indicating that the club face of a golf club head is the point of maximum stress.
In order to address this issue of connecting a face insert to the body of the golf club head at an area that has the highest stress levels, it is not uncommon for golf club designers to utilize a strong bonding process such as perimeter welding to affix the face insert to the body of the golf club head. U.S. Pat. No. 6,669,577 to Hocknell et al. ('577 patent) discloses such an approach by initially stating the premise that high performance drivers employ relatively thin, high strength face materials that need to be attached to the body of the golf club head. The '577 patent then goes on to state that these faces are either formed into the curved face shape then are welded into a driver body component around the face perimeter or forged into a cup shape and connected to a body by either welding or adhesive bonding.
Hence, as it can be seen from above, despite all the advancement in utilization of face insert, the current art has been unable to sufficiently address this durability issue associated with the connectivity of the face insert with the body of the golf club head in a manner that does not involve excessive perimeter welding. The connection methods used by the current art involve extensive and excessive welding similar to those discussed in the '577 patent, and these methods of excessive perimeter welding generate excessive weight that may hinder the performance of the golf club head itself. Ultimately, it can be deduced that there is a need in the art for a golf club wherein the face insert is connected to the body of the golf club in an unconventional method that is less clunky and burdensome. More specifically, there is a need in the art for a golf club with a face insert wherein the face insert can be connected to the body of the golf club in a way that eliminates the unnecessary bonding weight while at the same time maintain the strength and durability to withstand the impact of a golf ball.